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This is my visual novel daughter K-T and I love her so much

#BABY #not lovestruck #what the fuck is this game called #lu lunchtime games club #i think???#k-t

The boundary clay

One of the distinct features of the boundary between the Cretaceous and the Tertiary (paleogene) in the geologic record is found in this photo. Sandwiched in the middle of this section, you see what is called the “boundary clay” layer.

66 million years ago at the end of the Cretaceous, a rocky asteroid hit the Earth off the shore of the Yucatan peninsula. Near the site of the impact, rocks were tossed around by enormous waves creating tsunami-caused deposits several meters thick in places like Cuba.

Away from the impact site, a variety of other things happened. The ash from that impact blotted out the sun and took years to rain out, causing rapid and catastrophic shifts in the climate. The change in climate caused changes in rock types that appear and then, in some places, suddenly disappear, as you see here. Many things died in the time window represented by that small layer, but after the catastrophe was over, sedimentation returned to mostly what it was doing pre-impact.

This rock comes from an exposure of the boundary in Wyoming. One of the distinct characteristics of this extinction is that the boundary clay is enriched in elements that aren’t abundant in the Earth’s crust. When the Earth formed, many elements sank along with iron metal and sulfide into the Earth’s core, depleting the surface layers of those elements. One of those elements, Iridium, is enriched by a factor of 1000x in that layer relative to the rocks around it; measurement of that iridium anomaly was the key step in realizing that these global boundary clay layers had to be caused by an impact.

There are many mass extinctions in Earth’s history and the Cretaceous is not the biggest. However, it is the only one we can tie fairly directly to an impact. The end-Permian extinction was bigger; many more species died and life took ~10 million years to recover from that calamity, but so far there is little to no evidence of a similar “boundary clay” layer or similar chemical fingerprints of an asteroid impact associated with any other extinction. The K-Pg boundary extinction thus may be a unique event in Earth’s history, at least over the last 500 million years.

-JBB

Image credit: Wikimedia Commons http://en.wikipedia.org/wiki/File:K-T-boundary.JPG

#Geology #boundary clay #k-pg #K-T #science #wyoming #sediment #asteroid #bolice #cretaceous #dinosaur #extinção #ion #the earth story

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· natgeo@RobertClarkphoto People may disagree but I think that this picture is a beautiful thing, not because of the photography or because it looks like a painting by a modern art master, but because of what it is, and how it relates to the earth and to the modern life that we all enjoy. What is it? It is a slice of rock from Canada, representing a span of 500,000 to 750,000 years, offers clues to what the world was like before, during, and after the meteor struck Earth. A. Before the impact (Cretaceous): The transition from pale mudstone to coal shows the climate shifting from dry to wet, perhaps stressing dinosaurs, other fauna, and flora. B. Impact (66 million years ago): No dinosaur fossils are found in or above this layer. Cracked quartz and rare metals such as iridium (scarce on Earth but plentiful in some meteorites) suggest a meteor strike. C. After the impact (Paleogene): Microfossils in coal indicate that forests collapsed and ferns took over. Before the impact on the bottom of the rock is revealing a change in climate, shifting from a dry to wet environment. The center section where you can see the earth colored thin line is the time of the asteroid impact 66 million years ago, and the top section is a layer of the ash that covered the planet which leads to the death of most dinosaurs and the rise of Mammals. Where does the name come from? The first segment of the Cenozoic Era, from 65 million years ago until the present, has historically been called the Tertiary Period. The abbreviation for the boundary between the Cretaceous and Tertiary periods is the K-T boundary, where K is the abbreviation for the German form of the word Cretaceous. Thank you to the @RoyalTyrrell Museum......for allowing me to photograph this specimen. #Dinosaurs #mammals #astroid